Vacuum valves are useful for manipulating a work piece in pick and place applications. An external pressure source is applied to the valve which typically has a suction head attached, the suction head is contacted to the work piece, which is then lifted depending on the porting of vacuum pressure through the valve. Alternate valve designs have evolved to increase the efficiency of the use of vacuum pressure. Two designs include dual flow and tri-flow type valve designs.
Dual flow valves are generally limited to a small fluid flow through an orifice and are preferred in applications when suction heads many not be in sealing contact with the work piece. Because of the small fluid flow rate, dual flow valves will limit vacuum pressure loss to the orifice flow when sealing contact is not met with the work piece. However, the small fluid flow rate limits dual flow valves to applications involving non-porous work pieces.
Try-flow valves are not limited to a small fluid flow orifice flow rate and therefore offer greater utility at the expense of greater complexity. Tri-flow valves generally have a full-open vacuum state that permits the application of the full vacuum potential applied to a valve. Moreover, the inclusion of a flow sensor enables the tri-flow valve to determine when a suction head has not made sealing contact with the work piece and decrease the leakage of the tri-flow valve to the orifice flow rate.
With either of the above discussed dual-flow or tri-flow valve, there is always an inherent leakage if a non-sealing contact is made with the work piece. It would be desirable to eliminate or minimize the orifice flow rate leakage in pick and place applications to conserve vacuum pressure and the energy required to create vacuum pressure. This inherent undesirable characteristic of the above valve designs is further aggravated when an array of dual-flow and/or tri-flow valves are working in parallel off the same vacuum generator.
A further undesirable characteristic of the above valves designs is the necessity to have visual confirmation of contact of the suction head to the work piece prior to turning on the vacuum pressure. In other words, vacuum pressure is ordinarily not applied in a system including the above valve types until there is contact between the suction head and the work piece. It would instead be desirable to enable the valve with the functionality to determine the proper instant to apply vacuum pressure. Such functionality would further enable the saving of vacuum pressure in a pick and place application.